ABSTRACT Laser‐enhanced contact optimization (LECO) technology has attracted growing attention to further improve the photovoltaic conversion efficiency (PCE) of tunnelling oxide passivated contact (TOPCon) solar cells. Although LECO is known to improve metallization via current‐induced firing, the specific interaction between interfacial microstructure evolution, contact resistance, and carrier recombination remains not fully understood. Herein, we clarify the underlying mechanisms of silver‐silicon contact formation on the p + emitter during fast firing and subsequent LECO processing. We identify that a relatively low peak firing temperature followed by a secondary LECO treatment is more promising than increasing the firing temperature. Specifically, while the secondary LECO process leads to a slight increase in localized specific contact resistivity, it significantly increases the areal density of effective Ag–Si contact points, including Ag–Si alloy. This increased contact density compensates for the local resistivity rise through a parallel resistance network mechanism, ensuring efficient carrier extraction. Furthermore, unlike high‐temperature firing, which aggravates passivation damage, the secondary LECO acts as a localized annealing process, simultaneously minimizing metal‐induced recombination. Consequently, this optimized strategy endows the champion cell achieving a PCE of 26.69%. This work provides critical insight into balancing carrier transport and recombination, offering a promising route toward the development of high‐efficiency TOPCon solar cells.
Zuo et al. (Sun,) studied this question.